Just a suggestion Peter.
In my opinion the "load" on the engine is also a factor.
What signal? probably the MAP one.
I have seen LB as high as 83mph. (I have pictures to prove the theory. and can be done by anyone)
Of course this is on a G1.(manual)
(My opinion)

The load is of course a factor for LB, but I am not concerned with that in this mod though, as the load will be at the the same levels that allow LB at whatever speed. It won't be a factor that effects wether the VSS is the cut off when the load is at an acceptable level.

We are just testing the theory that all things being equal, with eng load at acceptable levels and engine rpm being low enough, that the hard LB cut off HCH1 UK manual cars have is due to the VSS signal indicating > 45mph. US manual cars operate LB upto ~65mph. I want the same facility.

Jonny

Having studied the Insight and HCH1 manuals there is no indication that the car has any idea what actual gear it is in via any sort of direct switch on the gearlever or gearbox. So that should not be a factor. It or possibly the gauge cluster may calculate what gear it thinks it is in from rpm and mph but that will probably only confuse the shift lights rather than the ECM itself. We shall see.

The CVT presents a tricker issue as according to the manual it has a secondary VSS sensor in the CVT transmission. (So that may require two gizmos) Also the CVT TCM is in close comms with the ECM at all times, which will probably pick up discrepancies between the various signals. So that may bring unexpected results. Also I don't own or have access to a CVT HCH1 so can't do much more about that. In fact I'm not sure they were even sold over here?

The manual seems to indicate the VSS signal is 5v so that makes the gizmo at little bit simpler.

If the mod works then for the Manual HCH1 and G1 insight it might mean we can extend the LB window when a hard VSS cut off is evident from how it works presently.

The circuit schematic I will be testing today is below. This is untested and first draught.
It will look pretty familiar to those who have the IMAC&C for the HCH1 as it shares a lot in common.
The button toggles the VSS mod on/off.

If it works looks like a candidate for the neat little IMAC&C HCH1 box

Edit

I'm just going to capture some VSS data using my logic analyser with car on axle stands in gear and accelerating upto 30mph/60mph so i can see what the signal looks like.

Well I captured some VSS data and have the gizmo built and wired in but now need to tweak the code as stupidly I had the logic wrong way round and was increasing the pulse frequency instead of reducing it Doh. Will try that this afternoon.

After fiddling around with car on axle stands set a few ECM error codes so had to reset codes (which also clears readiness data etc) so i need a few drive cycles to get back to all readniess codes OK.

I went for a simple to implement divide VSS pulses by two to start with, so 60mph actual is seen by ECM as 30mph. (It's a big ask I know but if that doesn't work i will go down to 60mph actual = 45mph) Drove round the block about 6 miles no error codes which was encouraging, but green shift up indicator was lit even though car was in 5th gear at say 45mph. No lean burn at all either at the moment. Need to implement the passthru code so i can check wether LB is working at all at the moment even in standard form, or if i need more stop/start cycles to get that re-enabled. Ran out of time today.

Speedo etc working correctly as the gauges are recieving the non molested VSS data, it is only the VSS input into the ECM which is being modified.

Well simply feeding the ECM with VSS / 2 pulses doesnt work, but I still haven't tried VSS / 1.5. (Code is harder than I thought) No error codes though but the gear change shift up light is on. So still got a few things to try.

1) VSS / 1.5

2) Changing VSS signal as soon as it leaves sensor so it is the same for all the devices on the car. Rather than just feeding the ecm with the modified signal. This will effect the speedo etc but there may be some relationship between all the modules that use the VSS and the ECM etc.

As an aside I managed 85mpg on a 140 mile round trip yesterday during this testing.
Decent weather and steady 50-55mph driving speed with background 10A assist and extra on hills. No lean burn though as above the threshold.

Sure looks like the lean burn secrets are going to say hidden a little longer.
But hopefully if the whole car is fooled with a false speed then surely it should trick lean burn mode into working.
Well done on the 85MPG!

It knows the gear from the rpm and VSS relationship. You can't really work around that and hence the shift light.

I did a lot of playing around on PGMFI.org with Crome and über data etc and the gear is known by the car as it does different trims and people were playing with different boost settings for the lower gears on boosted Hondas.

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